Method of fabricating a suspension load beam with a composite damping core

ABSTRACT

A suspension load beam used for attachment to a slider assembly and an actuation arm in a disc drive for data storage has a rigid middle beam section comprising a rigid bottom layer, a rigid top layer and a composite core layer sandwiched between the bottom layer and the top layer. A method for fabricating a vibration resistant mechanical member used a disc drive subject to high frequency motion operations is also disclosed. The method involves making an integral laminate structure and fabricating the mechanical member from the integral laminate structure. The integral laminate structure has a rigid bottom layer, a composite core layer on top of the rigid bottom layer, and a rigid top layer on top of the core layer so that the composite core layer is sandwiched between the rigid bottom layer and the rigid top layer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a division of application Ser. No. 10/610,788 filedJun. 30, 2003.

BACKGROUND

The present invention relates to a suspension load beam in a disc drive,such as a hard drive using a magnetic storage medium. More particularly,the present invention relates to a disc drive suspension load beam usinga damping material to reduce high frequency vibration.

Disc drives are one of the key components to store data in a computersystem. In a basic hard disc drive, data is stored in a magnetic mediumformed on a surface of a rotating disc. The hard disc drive reads andwrites information stored on tracks on a disc bearing the magneticmedium. To do this, a read/write head that includes a transducer carriedby a slider assembly is placed in close proximity to the surface of themagnetic medium. The slider is attached through a gimbal system to adistal end of a suspension load beam. The proximal end of the suspensionload beam is attached to an actuator arm which is rotatably controlledby a voice coil motor (VCM). The disc drive system sends control signalsto the voice coil motor to move the actuator arm and the suspensionsupporting the read/write head across the disc in a radial direction tothe target track. The positioning of the read/write head over themagnetic medium is controlled by a closed loop circuit for betteraccuracy. In addition to the active controlling signal from the closedloop circuit, the precise positioning of the read/write head is affectedby a dynamic balance between two vertical forces. The first force is agram load applied by the suspension load beam to bias the head towardthe disc surface. The second force is an air bearing lifting forcecaused by the fast motion between the slider and the disc surface.Roughly, the looped control system controls tracking (i.e., radialpositioning of the head) while the dynamic balance determines fly-height(i.e., head-media spacing). However, as the areal density of concentricdata tracks on magnetic discs continues to increase (that is, the sizeof data tracks and radial spacing between data tracks decrease), harddisc systems also use active control for more precise verticalpositioning of the head.

One of the most significant adversarial conditions affecting precisepositioning of the read/write head in a disc drive system is vibration,particularly that caused by head suspension resonance. Many types ofvibration exist in a disc drive system to cause fluctuation of themagnetic read/write head positioning. However, vibrations that occur atfrequencies far away from a resonant mode (e.g., less than one third ofthe first resonant mode) are usually less serious concerns. In contrast,vibrations that cause resonance of the system are often much moreserious obstacles in improving areal density and rotation speed of thedisc drive system. Every closed loop servomotor system has apredetermined bandwidth in which resonances occurring within thebandwidth degrade the performance of the servomotor system. In a harddisc drive system, for example, windage (fluid turbulence caused byairflow) and head vibration occur at a frequency close to a resonantmode of the suspension load beam and thus cause the suspension headassembly to resonate at large amplitudes. Windage and head vibration,however, are not the only sources that cause resonance in a hard discdrive system. In today's high-speed hard disc drives, the servomotorthat moves the parts at high frequency may also cause resonance. Inaddition, when it is desired to position the magnetic head at a specifictrack location, the voice coil motor is driven by a voltage that has avery short rise time to accelerate the actuator very quickly. Once theactuator is in motion, the voltage levels off and the actuatorapproaches a constant velocity. As the actuator approaches the targetlocation on the disc, a similar, but inverse abrupt voltage pattern isapplied to the voice coil motor to stop the suspension actuator. Thissequence of voltage change is best represented by a square wave, whichis a superposition of many waves of different frequencies, according toFourier transform. The operation of the servo system in a hard discdrive to move the suspension head assembly thus has inherent frequencycomponents that may excite resonance.

Resonance degrades the performance of a disc drive in several ways.First, severe resonance, especially that of torsion or sway mode, maycause the magnetic read/write head to move away from the target trackand thus result in data reading/writing error. Second, resonance in thevertical direction, such as that caused by resonance in bending mode,may cause fluctuations in the fly height of the read/write head toresult in data error as well. In extreme cases, vertical fluctuationsmay even cause catastrophic damage of the disc drive due to directcontact between the head and the disc surface. Third, during resonance,the transducer element of the read/write head is forced to modulate,causing a significant decrease in the signal to noise ratio of thesystem and increase of the non-repeatable run-out (NRRO).

Significant efforts have been made to alleviate the problem ofresonance. Various methods have been used. Optimization of the system isessentially a balance of several factors, often gaining on one aspect ata cost of sacrificing another, as commonly found for aspring-mass-damper system. A suspension load beam must be sufficientlystiff in order to be mechanically and structurally stable. Unstablematerials suffer change of physical dimension with time, so-called coldflow or creep. To maintain a sufficient stiffness of the suspension loadbeam, a stiff metal piece, such as stainless steel sheet material, isused to make at least part of the suspension load beam. In principle,stainless steel part of the load beams could be made thicker to increasethe bending and torsion mode frequencies, but the greater masssignificantly degrades the performance of the actuator assembly byincreasing the inertia of the arm. An increased inertia will decreasethe access time to position between data tracks and increase the currentrequirements necessary to move the voice coil motor and the suspensionhead assembly. These changes then cause other problems such as increasedheat within the disc enclosure and increased power requirements. Athicker steel arm will also result in a higher mass assembly that willcause significant degradation of shock resistance of the disc drivesystem. Higher mass also leads to lower stability. Although materialshaving higher stiffness/mass ratio than that of stainless steel do existand have been experimented, solutions of this type have not becomewidely acceptable mainly due to high cost and low reliability issues.Other methods for increasing the stiffness of the suspension load beamwithout increasing the mass or switching to a more expensive materialare also suggested. U.S. Pat. No. 5,408,372 to Karam, for example, usesa micro-stiffening technique to control resonance in the suspensionsystem of a disc drive.

Another approach to reduce resonance of the suspension head system in adisc drive is to use dampers. U.S. Pat. No. 3,725,884 to Garfien shows asupport arm on which the magnetic head is supported by a spring memberand up and down motion of the magnetic head is damped by an additionalleaf spring in rubbing contact with friction pads. U.S. Pat. No.4,760,478 to Pal et al. uses a layer of damping material fixed to thetop of the elongated flat load beam and a constraining member fixed incontact with the damping material to reduce the resonance. U.S. Pat. No.6,297,933 to Khan et al. discloses a disc drive suspension load beamhaving a damping structure containing an organic damping material. Thedamping structure is attached in a load beam recess sized and shaped tolimit exposure of organic damping material to the ambient atmosphere.

Dampers commonly used are damping structures attached to the suspensionload beam. Dampers are believed to absorb vibration energy whenrepetitive deformation (caused by vibration) of a material is dissipatedthrough internal energy losses, usually in the form of heat. One form ofinternal energy dissipation is through shear energy absorption in thelayer of damping material. It has been known that materials that exhibita large ratio of dynamic loss moduli to dynamic storage moduli, tan δ,tend to have high shear energy absorption and thus are good candidatesfor making dampers. An exemplary type of materials exhibit a large tan δis viscoelastic materials, which when deformed, have a stressproportional to both the deformation and the rate of deformation.Viscoelastic materials also exhibit creep and relaxation behavior. Creepmeans that under constant stress the deformation increases in time.Relaxation means that under constant fixed deformation the stressdecreases steadily in time. These properties generally relate closely todamping properties because they are opposite to that of a springmaterial which is known to preserve dynamic energy during motionswithout converting the energy into thermal energy.

A number of approaches have been taken to achieve material propertiessufficient for damping purposes. Specialized formulations ofcross-linking polymers have been developed which exhibit damping inspecific applications. Epoxy formulations have been developed fordamping vibrations in magnetic read/write heads, as disclosed in U.S.Pat. No. 5,270,888. Acrylic copolymers for damping are commerciallyavailable in, for example, sheeting form. Silicone chemistries have beendeveloped for damping, as disclosed in U.S. Pat. No. 5,434,214 to Suttonet al. In addition, a composite damping material is suggested in U.S.Pat. No. 5,965,249, in which a highly viscous damping fluid is entrappedwithin the pores of a porous material (such as an expanded polymer, feltmaterial, foam, fabric, metal, etc.). The patent further suggestsattaching a piece of the composite damping material to a surface of amechanical member in a disc drive to reduce vibration.

As suggested in U.S. Pat. No. 5,965,249, however, dampers used forreducing suspension head resonance are conventionally affixed separatelyon a surface (e.g., top surface) of the suspension load beam, typicallyusing an adhesive, instead of being formed as an integral part of thesuspension load beam. This is in line with the conventional concept ofsuspension damping in which the stainless steel part of the beam isconsidered the base structure to provide stiffness and mechanicalintegrity, while an add-on damper is considered to provide damping only.To achieve this goal, much effort has been made to provide a damper thatdoes not cause significant structural mortification of the basestructure.

In order to maximize the shear energy absorption in the dampingmaterial, elaborate designs of using a constraining member have beenproposed. For example, U.S. Pat. No. 5,594,607 to Erpelding et al.discloses a laminated suspension having a stainless steel stiffenerlayer, a top constraining layer (which also functions as a conductorlayer), and a viscoelastic dielectric damping layer, wherein theconstraining layer has a pattern of land areas etched thereon toincrease the shear energy absorption in the damping layer.

Using a different approach, U.S. Pat. No. 5,187,625 to Blaeser et al.proposes a head suspension load beam which incorporates a layer ofdamping material throughout the entire structure of the suspension toreduce the amplitude of all resonant modes of vibration. It is believedthat because the point on the suspension structure at which maximumstrain energy occurs may change for each mode of vibration, it isadvantageous to distribute the damper throughout the entire structure inorder to cover all possible vibration modes. However, the use of thedamping material layer throughout the entire suspension structure isstill in line with the conventional concept of suspension damping inwhich the base structure of stainless steel provides stiffness andmechanical integrity while the add-on damper provides damping.

In yet another different approach, alloys having high intrinsic dampingproperties have been proposed to replace the conventional stainlesssteel to make suspension load beams in a disc drive. An example of suchalloys is found in U.S. Pat. No. 6,361,740.

At the same time, with the increasing demand for disc drives that aremore reliable, quieter and faster, and have larger storage capacity(with increased areal density) and sometimes smaller overall disc size,there is an increasing need for a disc drive suspension system havingbetter balanced optimization between several performance propertiesincluding damping property, stiffness and the structural integrity.

SUMMARY

The present invention is a suspension load beam used for attachment to aslider assembly and an actuation arm in a disc drive for data storage.The suspension load beam has a front beam section connecting to a sliderassembly carrying a transducer head, a rear beam section connecting toan actuation arm, and a rigid middle beam section located between thefront beam section and the rear beam section. The rigid middle beamsection comprises a rigid bottom layer, a rigid top layer and acomposite core layer sandwiched between the bottom layer and the toplayer. The composite core layer comprises a damping material and a rigidmaterial and is coextensive with the rigid bottom layer. In oneembodiment, the composite core layer is a multilayer laminate structurehaving a layer of the damping material and a layer of the rigidmaterial, the two layers being coextensively laminated together.

The present invention is also a method for fabricating a vibrationresistant mechanical member used a disc drive subject to high frequencymotion operations. The method comprises the following steps: providing afirst rigid layer; laminating a composite core layer on the first rigidlayer, wherein the composite core layer comprises a damping material anda rigid material; laminating a second rigid layer on the core layer sothat the composite core layer is sandwiched between the first rigidlayer and the second rigid layer to form an integral laminate structure;and fabricating the mechanical member from the integral laminatestructure, so that the mechanical member has a desired size and shapefor each individual layer of the integral laminate structure. In oneembodiment of the method, the composite core layer is a multilayerlaminate structure having a layer of the damping material and a layer ofthe rigid material, the two layers being coextensively laminatedtogether.

The invention utilizes a realization that, instead of addressing thestiffness and mechanical integrity of the suspension load beam and itsdamping property separately by adding dampers to the main structure ofthe suspension load beam, a composite material having both a structuralelement and a damping element is used to form the core of the suspensionload beam to achieve balance and optimization in both above respects atthe same time.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further explained with reference to thedrawing figures listed below, wherein like structure is referred to bylike numerals throughout the several views.

FIG. 1 is a perspective view of a disc drive including an actuationsystem for positioning a slider over tracks of a disc.

FIG. 2 is a schematic view of a suspension load beam in accordance withthe present invention.

FIG. 3 is a cross-sectional view of FIG. 2 along section 3-3.

FIG. 4 is an enlarged view of an embodiment of the composite core layerin FIG. 3 in accordance with the present invention.

FIG. 5 is an enlarged view of a second embodiment of the composite corelayer in FIG. 3 in accordance with the present invention.

FIG. 6 is a schematic view of a variation of the suspension load beam inFIG. 2.

FIG. 7 is a schematic view of a second variation of the suspension loadbeam in FIG. 2.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of a prior art disc drive 10 which includesvoice coil motor (VCM) 12 arranged to rotate actuator arm 16 on spindlearound axis 14. Head suspension load beam 18 is connected to actuatorarm 16 at head mounting block 20. Flexure 22 is connected to a distalend of head suspension load beam 18, and carries slider 24. Slider 24carries a transducing head (not shown in FIG. 1) for reading and/orwriting data on disc 27, which rotates around axis 28 and includesconcentric tracks 29 on which the data is written.

FIG. 2 shows more details of an embodiment of suspension load beam 18 inaccordance with the present invention. Suspension load beam 18 has frontbeam section 30 spanning longitudinally the range denoted by “a”, middlebeam section 32 spanning longitudinally the range denoted by “b”, andreader beam section 34 spanning longitudinally the range denoted by “c”.In this description, the longitudinal direction is along theconventional length of the suspension load beam. On middle beam section32 are a pair of side rails 35 to further stiffen that section. On rearbeam section 34 is mounting hole 36 for attaching suspension load beam18 to actuator arm 16 (FIG. 1) and the mounting block 20 (FIG. 1). Theattaching mechanism, commonly a swaging mechanism as known in the art,is not essential to the present invention. On front beam section 30 ismatching registration opening 38 for mounting slider 24 (FIG. 1),commonly using a flexure and gimbal mechanism as known in the art. Themechanism for mounting slider 24 on suspension load beam 18 is notessential to the present invention. Furthermore, structural appearanceof suspension load beam 18 in FIG. 2, such as matching registrationopening 38, side rails 35 and mounting hole 36 are nonessential for thepresent invention.

FIG. 3 is a sectional view of FIG. 2 along section 3-3. As shown in FIG.3, middle beam section 32 has three layers. Bottom layer 40 is a rigidsupport layer made of stainless steel having a nominal thickness ofabout 1 mil (0.001 in., or 0.0254 mm). Top layer 42 is another rigidsupport layer similar to bottom layer 40, made of stainless steel havinga nominal thickness of about 1 mil (0.001 in., or 0.0254 mm). Sandwichedin the middle of bottom layer 40 and top layer 42 is composite corelayer 44 having a nominal total thickness of about 4 mils (0.004 in., or0.102 mm). The three layers, 40, 42 and 44, are laminated together toform a sheet structure constituting middle beam section 32.

FIG. 4 and FIG. 5 show further details, in two different embodiments 44Aand 44B, of composite core layer 44 in FIG. 3. As distinguished fromprior art structures in use or disclosed, the core layer 44 is made of acomposite material having at least two different materials (phases)instead of a damping material only. In a two-phase combination, thefirst phase material is a rigid material such as resin, epoxy,polyolefin, polyurethane, polyethylene or polyamide in solid or glassstate. This phase is to contribute to the structural stability ofsuspension load beam 18 by virtue of its stiffness. The second phasematerial is a damping material that demonstrates a desirable dampingproperty. Any damping material, as long as it can form a stablecomposite with the first phase material may be used. As it has beenknown in the art, materials that exhibit a large ratio of dynamic lossmoduli to dynamic storage moduli, tan δ, tend to have high shear energyabsorption and thus are good candidates for making dampers. An exemplarytype of materials exhibit a large tan δ is viscoelastic materials. Thesematerials, when deformed, have a stress proportional to both thedeformation and the rate of deformation. An example of a suitableviscoelastic material is the family of Scotchdamp brand SJ2015X, such asISD 110 as identified by the manufacturer, available from 3M Corp. inSt. Paul, Minn. Many other materials, particularly polymers such aspolyamide, epoxies, silicones, polyurethanes, fluorocarbons waxes,acrylics, demonstrate damping properties. In general, a polymer that isnear or above its glass transition temperature may be used for thesecond phase material in composite core layer 44 in accordance with thepresent invention.

There are many ways to form a composite of two or more phases. As knownin the art of making composites, two-phase composites can be combined in10 unique configurations. Among these unique configurations, the 0-3 and2-2 configurations are the most common. In the 0-3 configuration, asreflected by the name of this configuration in which each digitindicates the number of dimensions a corresponding phase is connected toitself, the first phase material is connected in three (3) dimensionswith itself and the second phase material is not connected in anydimension (i.e., zero dimension) with itself. In the 2-2 configuration,the first phase material and the second phase material are eachconnected in two dimensions with itself.

FIG. 4 is an enlarged view of composite core layer 44 in FIG. 3 having0-3 configuration in accordance with the present invention. Thecomposite core layer having this specific configuration is denoted as44A. In this embodiment, the first phase material is denoted as 46 whilethe second phase material is denoted as 48. The first phase material 46comprises a continuous rigid material, and the second phase material 48comprises discrete particles of the damping material dispersed in thefirst phase material. An example of this 0-3 composite configuration hasa porous material such as polymer, foam, fabric or metal as the firstphase material with particles of the second phase material, aviscoelastic damping material, entrapped in the pores of the first phasematerial.

FIG. 5 is an enlarged view of composite core layer 44 in FIG. 3 having2-2 configuration in accordance with the present invention. Thecomposite core layer having this specific configuration is denoted as44B. In the embodiment illustrated, composite core layer 44B has alaminated composite structure in which a rigid material (first phasematerial) layer 54 has a nominal thickness of about 3 mils (0.003 in.,or 0.0762 mm) is sandwiched between two much thinner damping material(second phase material) layers 50 and 52 each having a nominal thicknessof about 0.5 mil (0.0005 in. or 0.0127 mm).

Although the 2-2 composite configuration shown in FIG. 5 has two dampingmaterial layers 50 and 52 separated by rigid material layer 54, thesimplest possible 2-2 composite configuration may require only onedamping material layer and one rigid material layer only, omitting oneof damping material layers 50 and 52. Alternatively, multiple rigidmaterial layers and multiple damping material layers may be laminatedtogether in a sequence alternating between the two material phases(rigid material and damping material).

Suspension load beam 18 of FIG. 2 having middle beam section 32 that hascomposite core layer 44 sandwiched between two rigid top and bottomlayers 42 and 40 can be made by a number of possible methods, primarilylamination methods. Composite core layer 44, two embodiments of which(44A and 44B) are illustrated with more details in FIG. 3 and FIG. 5,may be separately formed first and then applied on bottom layer 40,followed by the application of top layer 42 on composite core layer 44.The lamination of two contacting layers (bottom layer 40 and compositecore layer 44, or top layer 42 and composite core layer 44) may berealized by a number of ways, including heating, mechanical means suchas pressure or binders, or through an adhesive. When an adhesive isused, a separate adhesive layer (not shown) may be used between the twocontacting layers. Alternatively, in the embodiment having a laminatedmultiple layer composite core 44B shown in FIG. 5, one or both dampingmaterial layers 50 and 52 may also be an adhesive at the same time,facilitating direct binding to their contacting layer (bottom layer 40and top layer 42, respectively) without requiring additional adhesivelayers.

The embodiment having a laminated multiple layer composite core 44Bshown in FIG. 5 may be alternatively made by sequentially laminating alllayers (40, 50, 54, 52 and 42) starting from bottom layer 40, instead offorming composite core 44 first and subsequently laminating compositecore 44B on bottom layer 40.

Although suspension load beam 18 may be fabricated individually, it canalso be made in batch form. To do this, lamination of a size much largerthan that of an individual suspension load beam is made first and thencut into smaller pieces for individual suspension load beams. Furtherfeatures such as side rails 35 (FIG. 2) can then be formed an individualsuspension load beams. A number of cutting methods known in the art,including etching, ion milling and direct slicing using a blade, may beused.

As shown in FIG. 3, damping material layer 44 and rigid bottom layer 40are coextensive in the lateral direction of cross-section line 39 (FIG.2). Damping material layer 44 and rigid bottom layer 40 may also becoextensive in the longitudinal direction along the length of load beam18 in the range devoted by “b” in FIG. 2. Coextensiveness between thesetwo layers in either direction is not required by the present invention,but may be preferred due to manufacturing reasons. Because the presentinvention allows control of the thickness of each layers, such as theoverall thickness of composite core layer 44 and individual thicknessesof damping material layers 50 and 52 and rigid material layer 54 (FIG.5), there is no requirement to control or adjust the area of theselayers in order to achieve an optimized balance among mass, rigidity anddamping effect. In contrast, in prior art damping methods in which adamper is attached to a surface of the suspension load beam, controllingof the location, overall amount, and the size of the area over which thedamper covers is always a source of difficulties in manufacturing and acause of inconsistency.

Furthermore, although the above-described coextensiveness betweendifferent layers may be preferred during the process of lamination, theareas of each layer may be individually modified after laminationprocess is complete using methods such as etching commonly known in theart. Particularly, instead of using stainless steel top layer 42, adifferent rigid material such as a conductive material may be used astop layer 42 for a purpose other than structural reinforcement of theload beam. Etching subsequent to lamination on the top layer may benecessary, and possible in the method of the present invention, in orderto form patterns required for functions unique to the top layer. One ofthe advantages of using a composite core layer which has both a dampingcomponent and a rigid structural component according to the presentinvention is the ability to reduce the degree of reliance on structuralreinforcement contributed by components such as stainless steel. It istherefore possible that a stainless steel bottom layer together with thecomposite core layer together may have sufficient mass-stiffness-dampingperformance, leaving room for selecting a top layer to provide otherfunctionalities without being severely constrained bymass-stiffness-damping performance of the load beam.

The composite core in accordance with the present invention may be usedin combination of any other designs for suspension load beams. Forexample, the composite core may be used in suspension load beamsdisclosed in U.S. Pat. Nos. 6,157,522 to Murphy et al. and 6,392,843 toMurphy, which two patents are incorporated herein by reference.

Denotation and separate description of the three beam sections 30, 32and 34 in FIG. 2 is for the purpose of clarity of description only anddoes not suggest that the three sections have to be fabricatedseparately and then assembled together. Rather, the entire suspensionload beam 18 may be fabricated as a single integral piece. For example,the three beam sections 30, 32 and 34 may share the same stainless steelbottom layer 40, making the three beam sections not only integral butalso partially unitary with respect to the shared stainless steel bottomlayer 40. In another embodiment, front beam section 30 has a rigid frontbottom layer, a rigid front top layer and a composite front core layersandwiched between the front bottom layer and the front top layer. Frontbeam section 30 and middle beam section 32 can be then unitary withrespect to all three layers. That is, front beam section and middle beamsection 32 may share a unitary rigid bottom layer, the unitary rigid toplayer and the unitary composite core layer, respectively.

In addition, although dimensions such as lengths in the longitudinaldirection of the three beam sections, and comparative dimensions such asratios lengths thereof are design choices that affect the overallperformance of the mass-spring-damping system, the suspension load beamaccording to the present invention is not limited to any specificdimensions are comparative dimensions and may be used in combination ofany additional design considerations.

Although FIG. 2 shows that only middle beam section 32 has side rails35, the feature of side rails are not essential for the presentinvention. Conventionally, side rails are formed on a section of loadbeam by bending an originally flat sheet (including the stainless steelsheet) in order to further stiffen that section. As shown in FIG. 2,side rails 35 are advantageously, but not necessarily, used to furtherstiffen middle beam section 32. Furthermore, the existence and thelocation of side rails 35 are not to be used as identification formiddle beam section 32. As shown in FIG. 6, both front beam section 30a, which has matching hole 38 a, and middle beam section 32 may haveside rails, or even unitarily share the same pair of side rails 35 a asshown.

Furthermore, although as shown in FIG. 2 front beam section 30 hasmatching hole 38 connecting to the slider assembly of the disc drive,the location of the matching hole 38 and connection thereby to theslider assembly are not an identification for front beam section 30. Asshown in FIG. 7, part of middle beam section 32 may also be used toconnect to the slider through matching registration opening 38 a. Theessence of the present invention, although described with regard tothree separate sections on the suspension load beam, is not a sectionaldesign of the suspension load beam, but rather the use of a compositecore in a stiff portion of the suspension load beam to integrallyachieve good damping property and mechanical integrity of the suspensionload beam.

The thicknesses of the layers in the illustrated embodiments are onlyillustrative. One of the advantages of using a composite core layer inaccordance with the present invention is the availability of moredesigning dimensions in which optimization may be made. Because thecomposite core has both a structural element and damping element, theconventional rigid layer is no longer the sole contributor to thestiffness and structural integrity of the load beam. As a result, moreroom of designing freedom is gained intensive the thickness of the rigidlayer and the selection of the material for making the same. Incontrast, the prior art method using a damping material as the core ofthe suspension load beam has no provision of a structural element forthe stiffness and mechanical integrity in the damping material core. Infact, while the prior art method has no intention to contribute to thestiffness and other mechanical properties of the suspension load beam byadding a damping material core, undesirable effects of an opposite kindmay be unavoidable, given that the suggested thickness (1 mil) of thedamping material core is comparable to the thickness of the stainlesssteel layer and constitutes about one third of the entire thickness (3mils) of the suspension load beam.

Compared to the prior art method using a damping material as the core ofthe suspension load beam, it is envisioned that much less amount ofdamping material is needed to achieve a comparablemass-stiffness-damping performance by using the composite core inaccordance with the present invention. For example, in the embodimentshown in FIG. 5, nominal thickness of each damping material layer 50 and52 may be significantly less than one fourth of the nominal thickness ofrigid material layer 54. In one embodiment, it is envisioned that rigidbottom layer 40 and rigid top layer 42 each have a thickness of 1 milinches (0.001 in. or 0.0254 mm) or less, composite core 44B (FIG. 5) hasan overall nominal thickness of about 4 mil inches (0.004 in. or 0.102mm) or less with a nominal thickness of about 3 mil inches (0.003 in. or0.076 mm) for rigid material layer 54, while damping material layers 50and 52 each have a much smaller nominal thickness of 0.5 mil inches(0.0005 in. 0.0127 mm) or less. Alternatively, one of damping materiallayers 50 and 52 may be replaced by a thin adhesive layer. For example,composite core 44B may have damping material layer 52 of a nominalthickness of about 1.0 mil inches (0.001 in. or 0.0254 mm), rigidmaterial layer 54 of a nominal thickness of 3 mil inch (0.003 in. or0.076 mm), and an adhesive layer of a nominal thickness of 0.2 milinches (0.0002 in. or 0.0051 mm) in place of damping material layer 50.It should be understood that within the spirit of the present invention,numerous combinations, both in terms of the layer sequence and layerthicknesses, are available. Given a certain ratio of layer thicknesses,the overall thickness of the load beam may be reduced to much less thanthe exemplary 5 mil-6 mil inches if necessary. Furthermore, depending onthe damping need and the damping characteristics of the damping materialused, damping material layer(s) much thinner than that of the aboveexamples may be used. Furthermore, when multiple damping material layers(such as layers 50 and 52 in FIG. 5) are used, these layers do not haveto have the same or a similar thickness. For example, layer 50 in FIG. 5may be a damping material layer having a nominal thickness of about 0.2mil inches (0.0002 in. or 0.0051 mm) and layer 52 in FIG. 5 may be adamping material layer having a nominal thickness of about 1 mil inches(0.001 in. or 0.0254 mm). Either or both of these damping materiallayers may also act as an adhesive layer.

Another aspect of the present invention relates to the realization thatdamping is only necessary during the operation of the disc drive andthat the operating temperature of the disc drive is usually above roomtemperature. The operating temperature of a typical have disc drive, forexample, is 45-75° C. This particular range of operating temperature isa relative consideration in material selections of both first phasematerial (rigid material) and second phase material (damping material)to make the composite core layer for a suspension load beam inaccordance with the present invention. For example, polymers such aspolyimides may be used for both first phase and second phase materials,as long as the polymer for first phase material remains rigid in thetemperature range of 45-75° C., or more narrowly 55-65° C., while thepolymer for second phase material becomes viscoelastic in the sametemperature range. Such selections of materials may be based upon theknowledge of the glass transition temperature of the polymer.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A method for fabricating a vibration resistant mechanical member, themethod comprising: providing a first rigid layer; laminating a compositecore layer on the first rigid layer, wherein the composite core layercomprises a polymeric viscoelastic damping material and a polymericrigid material; laminating a second rigid layer on the core layer sothat the composite core layer is sandwiched between the first rigidlayer and the second rigid layer to form an integral laminate structure;and fabricating the mechanical member from the integral laminatestructure, so that the mechanical member has a desired size and shapefor each individual layer of the integral laminate structure.
 2. Themethod of claim 1, wherein the composite core layer is a multilayerlaminate structure having a layer of the polymeric viscoelastic dampingmaterial and a layer of the polymeric rigid material, the two layersbeing coextensively laminated together.
 3. The method of claim 2,wherein the multilayer laminate structure of the composite core layer isformed first before the multilayer laminate structure is then laminatedon top of the rigid bottom layer.
 4. The suspension load beam of claim2, wherein the layer of polymeric viscoelastic damping material has athickness of 1 mil inches (0.001 in. or 0.0254 mm) or less.
 5. Themethod of claim 1, wherein the polymeric viscoelastic damping materialis interspersed and embedded within the polymeric rigid material.
 6. Thesuspension load beam of claim 1, wherein the bottom layer comprises astainless steel sheet material.
 7. The suspension load beam of claim 1,wherein the top layer comprises a stainless steel sheet material.
 8. Thesuspension load beam of claim 1, wherein the bottom layer has athickness of 1 mil inches (0.001 in. or 0.0254 mm) or less.
 9. Thesuspension load beam of claim 1, wherein the composite core has athickness of 5 mil inches (0.005 in. or 0.127 mm) or less.
 10. Thesuspension load beam of claim 1, wherein the damping material layer andthe rigid material layer each has a nominal thickness, the nominalthickness of the damping material layer being less than one fourth ofthe nominal thickness of the rigid material layer.
 11. The suspensionload beam of claim 1, wherein the polymeric viscoelastic dampingmaterial has a glass transition temperature below 75° C.
 12. Thesuspension load beam of claim 11, wherein the polymeric viscoelasticdamping material has a glass transition temperature below 55° C.
 13. Amethod of manufacturing a suspension member for a disc drive, the methodcomprising: forming a laminate structure including a composite corelayer sandwiched between a top layer and a bottom layer, wherein thecomposite core layer is formed of a polymeric rigid material and apolymeric viscoelastic damping material; shaping the laminate structureto form the suspension member.
 14. The method of claim 13, wherein thecomposite core layer has a 2-2 composite configuration.
 15. The methodof claim 13, wherein the composite core layer has a 0-3 compositeconfiguration.
 16. The method of claim 13, wherein shaping the laminatestructure includes at least one cutting operation.
 17. The method ofclaim 13, wherein shaping the laminate structure comprises: defining afront section for connecting to a slider assembly; defining a rearsection for connecting to an actuation arm; and defining a middlesection located between the front section and the rear section.
 18. Thesuspension load beam of claim 13, wherein the top and bottom layerscomprises stainless steel sheet material.
 19. The suspension load beamof claim 13, wherein the composite core has a thickness of 5 mil inches(0.005 in. or 0.127 mm) or less.
 20. The suspension load beam of claim13, wherein the damping material has a glass transition temperaturebelow 75° C.